JP2006174644A - Control unit for direct-current brushless motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controlling means for direct-current brushless motors that can brake a rotor with low noise when a motor is being rotated by external force. <P>SOLUTION: A control unit for direct-current brushless motors includes: a direct-current brushless motor 1; a magnetic pole position sensor 2 that detects the magnetic pole position of the rotor of the direct-current brushless motor 1; an inverter circuit 3 in which multiple switching elements are bridge-connected in three phases and which converts direct-current voltage 4 into alternating-current voltage by opening/closing of the switching elements and supplies it to the direct-current brushless motor 1; a controlling means 5 that opens and closes the switching elements based on the output signals of the magnetic pole position sensor 2; a bus current detecting means 7; and a PWM output turn-off means 8 that turns off the PWM signals based on the output of the bus current detecting means 7. The duty of the PWM signal outputted by the controlling means 5 is finely adjusted. Thus, even when a fan is being rotated by external force, it can be braked and stopped with low noise without imposing an excessive burden on a drive circuit or the motor. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for controlling a DC brushless motor.

  A DC brushless motor is often used to drive an outdoor fan of an air conditioner. The outdoor fan rotates when there is wind, and the rotation direction and speed are not uniform. If the motor is started in the rotation state, the motor may be heavily loaded depending on the rotation direction and rotation speed, and may be damaged in the worst case. There is.

  Therefore, if the outdoor fan is rotating at the start of operation of the air conditioner, the air conditioner is started after braking, stopping, and positioning.

  On the other hand, the DC brushless motor uses a magnetic pole position sensor to detect the magnetic pole position of the rotor. For braking, stopping, and positioning of the outdoor fan, the direction and the number of rotations are detected based on the output of the magnetic pole position sensor, and the current supplied to the stator winding is controlled accordingly. However, in the conventional driving device, since three magnetic pole position sensors are used, it has become a cause of increasing the cost.

Therefore, in Patent Document 1, for the purpose of reducing the cost, the motor is stopped after stopping the rotor at a predetermined position by performing direct current excitation or winding short-circuiting by the number of magnetic pole position sensors smaller than the number of winding phases. A technology to start is proposed.
Japanese Patent Application Laid-Open No. 10-290592

  However, when the external force acting on the motor is strong, the rotor cannot be stopped because the brake torque is weak when the winding is short-circuited. Moreover, since direct current excitation may or may not work depending on the position of the rotor, if the direct current excitation is weak, the rotor cannot be stopped and is shaken off.

  Although it is conceivable to increase the DC excitation in order to reliably stop the rotor, to increase the DC excitation, it is necessary to increase the amount of current flowing through the motor winding. When the amount of current flowing through the winding is increased, a strong magnetic field opposite to the direction of the magnetic field generated by the permanent magnet that forms the rotor is generated in the winding, causing the permanent magnet to demagnetize or to the inverter circuit. In the worst case, the device may be destroyed by excessive current stress.

  The present invention prevents the demagnetization of the permanent magnets constituting the rotor and the overcurrent of the inverter circuit in advance when the motor is rotated by an external force, and can reduce the noise and reliably brake the rotor. An object of the present invention is to provide a control device for a brushless motor.

In the DC brushless motor control device according to the present invention, a DC brushless motor, one magnetic pole position sensor for detecting the magnetic pole position of the rotor of the DC brushless motor, and a plurality of switching elements are connected in a three-phase bridge, An inverter circuit that converts a DC voltage into an AC voltage by opening and closing and supplies the DC brushless motor, a control unit that opens and closes the switching element based on an output signal of the magnetic pole position sensor, and a bus current detection unit that detects a bus current And a PWM signal off means connected between the control means and a driving means for driving a switching element based on an output signal of the control means, and for turning off the PWM signal for a predetermined time based on the output of the bus current detecting means. The control means includes the magnetic pole position sensor before starting the DC brushless motor. One of the switching elements on either the positive voltage side or the negative voltage side is PWM-energized in synchronization with the output signal of the servo, and one of the other switching elements is turned on to brake the rotor. .

  As a result, even when the fan is rotated by an external force, the two-pattern DC excitation by PWM energization is switched at a predetermined magnetic pole position, and the duty of PWM energization is controlled based on the result of the bus current detection means, thereby driving It is possible to brake and stop the DC brushless motor without applying an excessive load on the circuit and the motor and with low noise.

  The DC brushless motor control apparatus according to the present invention is low in noise and surely DC brushless, without imposing an excessive burden on the drive circuit and the motor, regardless of the rotation direction, even when the motor is rotated by an external force. The motor can be braked and stopped.

  In the first invention, a DC brushless motor, a magnetic pole position sensor for detecting a magnetic pole position of a rotor of the DC brushless motor, and a plurality of switching elements are connected in a three-phase bridge, and a DC voltage is converted into an AC voltage by opening and closing the switching elements. An inverter circuit that converts the signal into the DC brushless motor and supplies the DC brushless motor to the control circuit, and a control unit that opens and closes the switching element based on the output signal of the magnetic pole position sensor, a bus current detection unit that detects the bus current, And a PWM output off means connected between the driving means for driving the switching element based on the signal and turning off the PWM signal for a predetermined time based on the output of the bus current detecting means, the control means comprising a DC brushless motor Before starting, either the positive voltage side or the negative voltage side is synchronized with the output signal of the magnetic pole position sensor. By applying PWM current to one of the switching elements and turning on one of the other switching elements, it is possible to reliably brake and stop while preventing excessive current stress on the motor and inverter circuit. Become.

  According to the second invention, since the PWM signal for one carrier period can be turned off by setting the predetermined time of the first invention to be equal to or longer than the carrier period of the PWM signal, excessive current stress on the motor and the inverter circuit Can be prevented more reliably.

  According to a third aspect of the present invention, the control means changes the duty of the PWM signal based on a predetermined physical quantity, thereby causing an excessive increase in carrier sound due to a substantial decrease in carrier frequency due to the PWM signal being turned off for a predetermined time. The DC brushless motor can be reliably braked while preventing current stress.

  The fourth aspect of the invention increases noise with a relatively small burden on the microcomputer by setting the predetermined physical quantity of the third aspect of the invention to a signal level output to the control means when the PWM output off means turns off the PWM signal. Thus, the DC brushless motor can be reliably braked while preventing excessive current stress.

  In the fifth aspect of the invention, in particular, the predetermined physical quantity of the third aspect of the invention is increased by a simple configuration by setting the PWM signal output from the PWM output off means to the drive means as the time measured by the timer in the control means. Thus, the DC brushless motor can be reliably braked while preventing excessive current stress.

According to a sixth aspect of the present invention, in particular, the predetermined physical quantity according to the third aspect of the present invention is a sound detection means for detecting and outputting the sound of the DC brushless motor main body or its surroundings, thereby increasing noise and excessive current. It is possible to reliably brake the DC brushless motor while preventing stress.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
Hereinafter, a first embodiment in which the present invention is applied to a DC brushless motor that drives a fan provided in an outdoor unit of an air conditioner, for example, will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of a control device for a DC brushless motor according to Embodiment 1 of the present invention. In FIG. 1, a DC brushless motor 1 is used as a motor for driving an outdoor fan provided in an outdoor unit of an air conditioner. The U-phase, V-phase, and W-phase stator windings of the DC brushless motor 1 are neutral. A star connection is made at point N, and a magnetic pole position sensor 2 is provided on the stator. Among these, the U, V, and W phase windings of the stator are connected to the inverter circuit 3, and the connection points are U, V, and W, respectively. Further, the output signal line from the magnetic pole position sensor 2 is connected to the control means 5.

  In the inverter circuit 3, Qu, Qv, Qw, Qx, Qy, and Qz are three-phase bridge connected. That is, the series connection circuit of the switching elements Qu and Qx, the series connection circuit of the switching elements Qv and Qy, and the series connection circuit of the switching elements Qw and Qz are connected in parallel, and one end thereof is connected to the positive electrode of the DC power supply 4. The other end is connected to the negative electrode of the DC power supply 4 via the bus current detection means 7. These switching elements Qu, Qv, Qw, Qx, Qy, and Qz are connected to anti-parallel diodes Du, Dv, Dw, Dx, Dy, and Dz in antiparallel. Further, drive signals for Su, Sv, Sw, Sx, Sy, and Sz are output from the control means 5 to the PWM output off means 8, and in order to drive the switching elements Qu, Qv, Qw, Qx, Qy, and Qz, The output of the PWM off unit 8 is input to the driving unit 6.

  The operation of the first embodiment configured as described above will be described below. Here, the switching elements Qu, Qv, and Qw are referred to as positive voltage side switching elements of the inverter circuit 3, and the switching elements Qx, Qy, and Qz are referred to as negative voltage side switching elements of the inverter circuit 3. The magnetic pole position sensor 2 outputs a high level signal when detecting the N magnetic pole of the rotor, and outputs a low level signal when detecting the S magnetic pole of the rotor.

  2 (0) to (5) and FIGS. 3 (6) to (11), the internal structure of the DC brushless motor 1 and the magnetic pole position for every 30 degrees of rotation when the rotor has two poles and the stator has three slots. Indicates. 2 and 3, in order to simplify the explanation, the magnetic pole positions are equally divided into 12 and numbers 0 to 11 are assigned to define the magnetic pole position numbers and the positional relationship between the rotor and the stator. When the position of FIG. 2 (0), that is, the magnetic pole position where the output signal of the magnetic pole position sensor 2 falls from the high level to the low level is 0, and the rotation is in the normal rotation direction (the direction of the arrow shown), FIG. As shown in (0) to (5) and FIGS. 3 (6) to (11), the magnetic pole position shifts from 0 to 11 in ascending order.

  On the other hand, before the air conditioner is started, the outdoor fan that has been rotated by an external force such as natural wind needs to be temporarily stopped and positioned. Therefore, it is necessary to stop the brushless motor 1 by braking and positioning operations.

Therefore, as a method for braking the brushless motor 1, the control means 5 sends the drive signals Su, Sv, Sw, Sx, Sy, Sz through the PWM output off means 8 and the drive means 6 to the switching elements Qu, Qv, By adding to Qw, Qx, Qy, and Qz, one of the switching elements on either the positive voltage side or the negative voltage side is energized with PWM, and one of the other switching elements is turned on, and the PWM current is wound in the stator winding. There is a method in which a rotor is stopped by flowing a line and generating a magnetic field in a predetermined direction.

  As one pattern, consider the case where the positive voltage side transistor Qw of the DC power supply 4 is PWM-controlled and the negative voltage side transistor Qy of the DC power supply 4 is turned on. In this DC excitation pattern, a current path flows from the W point in FIG. 1 to the W phase winding, the neutral point N, the V phase winding, and the V point in FIG. A magnetic field is generated in the direction from the position 0 to the magnetic pole position 6. Due to this generated magnetic field, the rotor generates torque toward the magnetic pole position 3 shown in FIG. The DC excitation pattern for generating the torque is referred to as WY DC excitation in this specification.

  Further, in order to generate 180 ° reverse torque with the above-described W-Y DC excitation, PWM control is performed on the transistor Qv on the positive voltage side of the DC power supply 4, and the transistor Qz on the negative voltage side of the DC power supply 4 is turned on. Consider the case. In this DC excitation pattern, a current path flows from the V point in FIG. 1 to the V phase winding, the neutral point N, the W phase winding, and the W point in FIG. A magnetic field is generated in the direction from the position 6 to the magnetic pole position 0. Due to the generated magnetic field, the rotor is rotated by 180 ° in electrical angle with WY DC excitation, and torque is generated in the direction of the magnetic pole position 9 shown in FIG. This pattern of DC excitation is referred to herein as VZ DC excitation.

  A description will be given of the rotor braking control necessary for startup when rotating by an external force with reference to FIGS. 2 (0) to (5) and FIGS. 3 (6) to (11). In order to apply a braking torque to the rotor, it is necessary to apply DC excitation according to the magnetic pole position of the rotor. For example, when rotating in the normal direction and the magnetic pole position is in FIGS. 2 (3), (4), (5) and FIGS. 3 (6), (7), (8), (9) When W-Y DC excitation is applied, braking torque can be generated in the rotor. However, when the magnetic pole position is in (9), (10), (11), FIG. 2 (0), (1), (2), (2), (3) in FIG. If this is applied, acceleration torque will be generated in the rotor.

  On the other hand, in VZ DC excitation, torque is generated in the reverse direction (180 °) with respect to WY DC excitation, so the magnetic pole positions are shown in FIGS. 3 (9), (10), (11), and FIG. ), (1), (2), (2), and (3), the rotor can generate braking torque, but the magnetic pole positions are shown in FIGS. 2 (3), (4), (5), and FIG. 3 (6), (7), (8), (9), acceleration torque is generated in the rotor.

  Therefore, by switching and outputting two patterns of DC excitation of WY DC excitation and VZ DC excitation, braking torque can be continuously applied during one rotation of the rotor, even when the external force is strong. The rotor can be reliably braked.

  Hereinafter, a control method for switching between two patterns of DC excitation will be described. As described above, the DC excitation of the two patterns needs to be switched according to the magnetic pole position of the rotor. In the first embodiment, as shown in FIGS. 2 (0) to (5) and FIGS. 3 (6) to (11), the magnetic pole position sensor 2 is 30 more than the center of the V-phase winding in the normal rotation direction of the rotor. ° Provided in an eccentric position.

FIG. 4 shows a time chart of the rotor magnetic pole position, the output signal of the magnetic pole position sensor 2, and the DC excitation pattern output. First, when the output of the magnetic pole position sensor 2 is rotating in the normal rotation direction (hereinafter referred to as forward rotation), a falling low level is output at the magnetic pole position 0, and a rising high level is output at the magnetic pole position 6. Is output. A method for applying a DC excitation pattern for braking the rotor during forward rotation will be described below.

  First, an electrical angle of 90 ° was rotated from a position (magnetic pole position 3) rotated by an electrical angle of 90 ° from a position where the magnetic pole position sensor 2 falls (magnetic pole position 0) and a position where the output of the magnetic pole position sensor 2 rises (magnetic pole position 6). WY DC excitation is output until the position (magnetic pole position 9). Further, the rotor rotates and the position where the output of the magnetic pole position sensor 2 rises (magnetic pole position 6) is rotated from the position where the electrical angle rotates 90 ° (magnetic pole position 9) and the position where the output of the magnetic pole position sensor 2 falls (magnetic pole position 0). VZ DC excitation is output until the position rotated 90 degrees (magnetic pole position 3). By repeating this control, braking torque is applied to the rotor.

  On the other hand, with reference to FIG. 5, a description will be given of the braking control in the case of rotating in the direction opposite to the normal rotation direction by an external force (hereinafter referred to as reverse rotation). FIG. 5 shows a time chart of the rotor magnetic pole position, the output signal of the magnetic pole position sensor 2, and the DC excitation pattern output, as in FIG.

  During reverse rotation, the magnetic pole position shifts from 11 to 0 in descending order, and the output of the magnetic pole position sensor 2 rises at the magnetic pole position 0 and falls at the magnetic pole position 6. A method for applying a DC excitation pattern for braking the rotor during reverse rotation will be described below.

  First, an electrical angle of 90 ° is rotated from a position (magnetic pole position 3) rotated by an electrical angle of 90 ° from a position where the magnetic pole position sensor 2 falls (magnetic pole position 6) and a position where the output of the magnetic pole position sensor 2 rises (magnetic pole position 0). WY DC excitation is output between the positions (magnetic pole position 9). Furthermore, from the position where the rotor rotates and the output of the magnetic pole position sensor 2 rises (magnetic pole position 0) from the position where the electrical angle is rotated 90 ° (magnetic pole position 9) and the position where the output of the magnetic pole position sensor 2 falls (magnetic pole position 6) VZ DC energization is output up to the position (magnetic pole position 3) rotated by an electrical angle of 90 °. By repeating this control, the braking torque is applied to the rotor in the same way as during forward rotation.

  As described above, according to the output level of the output signal of the magnetic pole position sensor 2 of the rotor, the excitation torque can be applied to the rotor regardless of the rotation direction by selecting and exciting one of the two patterns of DC excitation signals. The braking torque can be reliably applied to the rotor without generating it.

  When the rotor is braked by the DC excitation of these two patterns, the cycle of the output signal of the magnetic pole position sensor 2 becomes long, and when the output level is fixed at the high level or the low level, the DC excitation of the two patterns is performed. The position of the rotor can be fixed, that is, stopped by continuing DC excitation by any pattern.

  In order to brake the rotor as described above, it is necessary to apply a braking torque stronger than the load torque due to the external force. Here, the braking torque is directly proportional to the winding current, and the winding current is directly proportional to the duty of the PWM signal output from the control means 6.

  On the other hand, in the first embodiment, in order to prevent excessive current stress on the motor winding and the inverter circuit, the bus current (the sum of the motor three-phase winding) is detected by the bus current detecting means 7 and the detected current is detected. The value is compared with the judgment current value set in advance in the PWM output off means 8 and when the power judgment current value is reached, the output of the PWM signal is controlled to be turned off for a predetermined time.

  Here, the determination current value of the PWM signal off means 8 is determined from the lower one of the demagnetization current of the motor winding or the maximum current allowable by the inverter circuit, and reaches the determination current value as shown in FIG. In this case, by turning off the output of the PWM signal for a predetermined time, the bus current can be made within a predetermined current value, and demagnetization of the motor and destruction of the inverter circuit can be prevented.

  Further, by setting the output off time of the PWM signal to at least one carrier cycle or more, it is possible to prevent the bus current from increasing in the broken line section (PWM signal on section) shown in FIG.

  Furthermore, the relationship between the braking torque and the duty of the PWM signal is shown in FIG. As shown in FIG. 7, the braking torque is saturated after the PWM signal off means 8 is operating, but by setting the PWM signal duty to a value greater than Dm that is greater than or equal to the required braking torque, It is possible to brake and stop while preventing an excessive burden.

  In the first embodiment, in order to simplify the description, as shown in FIGS. 2 (0) to (5) and FIGS. 3 (6) to (11), the rotor has two poles and the stator has three slots. However, the description so far also applies to a motor having 2n rotor poles and 3n stator slots (n is a natural number).

(Embodiment 2)
A second embodiment of the present invention will be described with reference to FIGS. 2 to 7 are the same as those in the first embodiment, and a description thereof will be omitted.

  FIG. 8 is a block diagram showing the configuration of the control device for DC brushless motor 1 according to the first embodiment of the present invention. In FIG. 8, the description of the same configuration as in FIG. 1 is omitted. In FIG. 7, the PWM output off means 8 has two systems as outputs, one being input to the driving means 6 and the other being input to the control means 5.

  The control means 6 increases the duty of the output PWM signal stepwise as shown in FIG. When the output duty of the PWM signal is increased, the bus current also increases. When the output of the bus current detecting means 7 reaches the determination current value at Dn shown in FIG. 9, the PWM output is turned off by the PWM output off means 8, The PWM off means 8 outputs a PWM off signal to the control means 6. When the PWM off signal is input, the control means 6 decreases the duty of the PWM signal by one step and sets the duty to Dn-1.

  Since the PWM signal is not repeatedly turned off by performing the operation of turning off the PWM signal for a predetermined time and the operation of reducing the duty after turning off as described above, the carrier of the PWM signal that is originally operated near the non-audible range A substantial decrease in frequency can be prevented. As a result, it is possible to prevent an increase in noise due to the carrier sound and to brake the DC brushless motor 1 without imposing an excessive burden on the inverter circuit and the motor.

(Embodiment 3)
A third embodiment of the present invention will be described with reference to FIGS. 2 to 7, FIG. 10, and FIG. 2 to 7 are the same as those in the first embodiment, and a description thereof will be omitted.

  FIG. 10 is a block diagram showing the configuration of the control device for DC brushless motor 1 according to Embodiment 3 of the present invention. 10, the description of the same configuration as in FIG. 1 is omitted. In FIG. 10, the PWM signal output from the PWM output off means 8 to the drive means 6 is input to the control means 5. The operation of the third embodiment configured as described above will be described below.

The control means 6 increases the duty of the output PWM signal stepwise as shown in FIG. When the output duty of the PWM signal is increased, the bus current increases, and when the output of the bus current detecting means 7 reaches the determination current value at Dn shown in FIG. The on section is the off section. The control means 5 receives the PWM signal that is the output of the PWM output off means 8 and measures the period of the PWM signal input by the internal timer. When the output of the bus current detection means 7 is less than the determination current value, the measured period is the carrier period as shown in FIG. When the output of the bus current detection means 7 reaches the judgment current value, the time measured by the timer of the control means 6 is twice or more the PWM carrier cycle. When a time longer than the carrier cycle is detected, the PWM signal Is reduced by one step to Dn-1.

  As described above, when the determination current value is reached, the operation in which the PWM signal on-period is set to the off-period for a predetermined time, and the operation in which the determination current value is reached is detected by the timer in the control means and the duty is decreased. By doing so, since the on period of the PWM signal is not repeatedly turned off, it is possible to prevent a substantial decrease in the carrier frequency of the PWM signal that is originally operated near the non-audible range. As a result, it is possible to prevent an increase in noise due to the carrier sound and to brake the DC brushless motor 1 without imposing an excessive burden on the inverter circuit and the motor.

(Embodiment 4)
Embodiment 4 of the present invention will be described with reference to FIGS. 2 to 7, 12, and 13. 2 to 7 are the same as those in the first embodiment, and a description thereof will be omitted.

  FIG. 12 is a block diagram showing the configuration of the control device for DC brushless motor 1 according to the fourth embodiment of the present invention. In FIG. 12, the description of the same configuration as in FIG. 1 is omitted. In FIG. 12, sound detection means 9 for detecting and outputting sound inside or around the DC brushless motor 1 is installed, and the output of the sound detection means 9 is input to the control means 5. The operation of the fourth embodiment configured as described above will be described below.

  The control means 5 increases the duty of the output PWM signal stepwise as shown in FIG. When the output duty of the PWM signal is increased, the bus current increases, and when the output of the bus current detection means 7 reaches the determination current value at Dn shown in FIG. Since the section is set to the off section, the carrier frequency f of the drive signal becomes about ½ f, the sound pressure having this spectrum increases, and the sound detection means 9 outputs a signal to the control means 5. As shown in FIG. 12, when the sound pressure level of the 1 / 2f spectrum is detected to be A or more, the duty of the PWM signal is decreased by one step to be Dn-1.

  As described above, when the determination current value is reached, an operation in which the on period of the PWM signal is an off period for a predetermined time, and an operation in which the duty is decreased when the sound pressure level of the 1 / 2f spectrum is detected as A or more. By doing so, since the ON period of the PWM signal is not repeatedly set to the OFF period, it is possible to prevent a substantial decrease in the carrier frequency of the PWM signal that is originally operated near the non-audible range. As a result, it is possible to prevent an increase in noise due to the carrier sound and to brake the DC brushless motor 1 without imposing an excessive burden on the inverter circuit and the motor.

  As described above, the DC brushless motor control device according to the present invention can perform braking with low noise without imposing an excessive burden on the inverter circuit and the motor when the fan is rotated by a relatively strong external force. Therefore, the present invention can be applied not only to the outdoor fan of the air conditioner but also to a brushless motor that freely rotates at the time of startup due to external factors.

The block diagram which showed the structure of the DC brushless motor control means in Embodiment 1 of this invention The schematic diagram showing the internal structure of the DC brushless motor in Embodiment 1 of this invention, and defining the magnetic pole position for every electrical angle 30 degrees The schematic diagram showing the internal structure of the DC brushless motor in Embodiment 1 of this invention, and defining the magnetic pole position for every electrical angle 30 degrees Time chart of DC excitation pattern during forward rotation in Embodiment 1 of the present invention Time chart of DC excitation pattern during reverse rotation in Embodiment 1 of the present invention Time chart showing the operation of PWM output stopping means 8 in Embodiment 1 of the present invention The characteristic diagram showing the relation between the duty of PWM signal and braking torque in Embodiment 1 of the present invention The block diagram which showed the structure of the DC brushless motor control means in Embodiment 2 of this invention Time chart showing the operation of the control means 5 in Embodiment 2 of the present invention The block diagram which showed the structure of the DC brushless motor control means in Embodiment 3 of this invention Time chart showing the operation of the control means 5 in Embodiment 3 of the present invention The block diagram which showed the structure of the DC brushless motor control means in Embodiment 4 of this invention Time chart showing the operation of the control means 5 in Embodiment 4 of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 DC brushless motor 2 Magnetic pole position sensor 3 Inverter circuit 4 DC power supply 5 Control means 6 Drive means 7 Bus current detection means 8 PWM output off means 9 Sound detection means

Claims (6)

A DC brushless motor, one magnetic pole position sensor for detecting the magnetic pole position of the rotor of the DC brushless motor, and a plurality of switching elements are connected in a three-phase bridge, and a DC voltage is converted into an AC voltage by opening and closing the switching elements, An inverter circuit supplied to the DC brushless motor, a control means for opening and closing the switching element based on an output signal of the magnetic pole position sensor, a bus current detection means for detecting a bus current, and an output signal of the control means and the control means And a PWM output off means for turning off the PWM signal for a predetermined time based on the output of the bus current detecting means, and the control means comprises the DC brushless device. Before starting the motor, synchronize with the output signal of the magnetic pole position sensor, Other control device of the DC brushless motor 1 a is turned on, characterized in that braking the said rotor of the switching element together with one of one of the switching elements of the compression side to PWM energization. 2. The control apparatus for a DC brushless motor according to claim 1, wherein the predetermined time is equal to or longer than a carrier cycle of the PWM signal. 2. The control apparatus for a DC brushless motor according to claim 1, wherein the control means changes the duty of the PWM signal based on a predetermined physical quantity. 4. The DC brushless motor control device according to claim 3, wherein the predetermined physical quantity is a signal level output to the control means when the PWM output off means turns off the PWM signal. 4. The control apparatus for a DC brushless motor according to claim 3, wherein the predetermined physical quantity is a time obtained by measuring a PWM signal output from the PWM output off means to the drive means by a timer in the control means. 4. The control device for a DC brushless motor according to claim 3, wherein the predetermined physical quantity is an output of a sound detection means for detecting and outputting a sound of the body of the DC brushless motor or its surroundings.

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